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New Scientist Live: why hasn’t the LHC found anything new?

The LHCb detector, deep below Geneva

M. Brice, J. Ordan/CERN

By New Scientist staff

Ten years ago today, the CERN’s Large Hadron Collider buried underneath Geneva, Switzerland, was turned on for the first time. The world’s largest particle smasher had been designed specifically to look for the Higgs boson, a particle first proposed by Peter Higgs and a clutch of other physicists in 1964. Four years later, CERN announced they’d finally discovered it.

But as physicist Tara Shears of the LHCb experiment will explain at New Scientist Live next week, that triumph was far from the end of the story. In fact, it raised far more questions than it answered.

The Higgs boson was proposed to fill in a crucial gap in our picture of the fundamental particles that make up matter: how they get the property of “thinginess” that we call mass. The Higgs and its associated field are something like an invisible, intangible molasses that fills all of space. Other particles stick to this molasses to varying degrees, and so acquire mass.

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With the discovery of the Higgs, our particle picture – the “standard model” – was complete. But the standard model is itself an incomplete description of matter. For a start, it only describes 4 per cent of the stuff we think must exist in the universe. The other 96 per cent comes in mysterious forms known as dark matter and dark energy, and the standard model is completely silent on what they might be.

Even more particles

Then there’s the enigma of the Higgs’s own mass. Quantum theory says the Higgs should interact with itself so much that its mass balloons to a truly humongous value. In fact, it was discovered to have a mass of just 125 gigaelectronvolts, just 130 or so times bigger than the mass of the protons and neutrons in the atomic nucleus. That’s chunky for a particle, but tiny compared with expectations.

Physicists came up with a cunning solution to all these problems – they invented new particles, a whole slew of them of them in fact. These “supersymmetric” particles partner the ones we already know, and interact with the Higgs in such a way as to rein in its mass, while also providing an identity for dark matter.

There’s only one problem: the LHC has detected no trace of these particles. Does that mean it is time to panic? At New Scientist Live on 23 September, Shears will give the lowdown on the latest research emerging from the tunnels of the LHC.